Step 5: Covering the Top of the Frame

Step 6: Installation

To install this frame, simply open the window and slide it inside up against the window framing. If you want to add extra stability to the installatio...

Many people have inexpensive air conditioners that are intended to fit into a double-hung (vertically sliding sash) windows and want to use them in horizontally sliding windows. If you already have some of these air conditioners or are attracted to them because their price tags are significantly lower than that of casement units, portable units, or central air, it is possible to make a frame to adapt them to sliding windows.

These solid, simple frames require no exterior brace. This is perfect for apartment dwellers and those who only need an air conditioner a few months of the year. It takes about an hour and some basic lumber and tools to construct these frames. Once built, your air conditioner can be installed and uninstalled in minutes. (Please note that window air conditioning units aren't intended to be permanently installed. These frames also make it simpler to remove them at the end of the warm season.)

The units pictured include unfinished plywood. However, this can be finished, painted or replaced with plexiglass or other materials, as the sheet lumber simply covers an opening and is not structural.

YOU NEED:
2X4s *(2 or less but the amount varies)
12 deck screws (or other long wood screws)
Drill
Saw
Screwdriver
Plywood Scrap

These window sills in the picture are fairly deep, allowing for the use of 2X4s. You may be able to substitute other lumber for shallower sills.

YAY! I have a window AC in my sliding casement window now! Thank you so much for the instructable, very easy to follow! The only thing I had to get differently was a more powerful drill because the cheapo I had wouldn't even go thru the wood without the battery dying. I used 1x1's for the frame with a 2x4 base standing upright (to clear the window frame) It's soooooo coool in my room now! Love it! Thanks again!

Great instructable. I moved into a highrise last year with side sliders and wasn't sure how I was going to mount an AC.

I picked up the materials at my Local Home Depot and had the cuts made there as well. The only tools required were a drill to pre-drill the holes and a screwdriver. The entire project cost about $70, $45 of which went toward two sheets of plexiglass and mini blinds. The second sheet of plexi diverts drips from above.

THANK YOU! My boyfriend and I used this guide to make a frame to fit in my windows for an A/C. Super cheap and easy. I had spent $32 on a proper "mounting frame" but it still seemed unsteady so we checked online and found your guide! The 2x4s only cost $6 and it took MAYBE an hour from first cut to last screw drilled in place. The best part is that I can take it with me when I move, and can help friends to make their own. To "pretty it up," I'm going to cover the wood with a painting/drawing of mine. I thought about painting it to match the walls, but it doesn't look bad at all really- and it WORKS!!

Ack, I just wanted to mention, that to get an angle for any water to drip out, once the sides and bottom were done, I held the A/C with the back tilted downwards a bit, and my boyfriend put the middle bar right on top and drilled it in place (from outside the frame in, of course). So instead of being straight, the middle bar is already at an angle. Also, we drilled the frame into 3 sides of the window sill - that sucker is going NOWHERE! (I mention it because I didn't quite understand your directions, although my boyfriend knew what you were talking about, lol) THANKS again.

The way you screwed in the center bar makes sense. Yeah, I can see that it might need to go in at an angle to keep the unit angled. I'm also glad that you guys figured out how to secure the frame. I'll bet that thing is solid! It makes me very happy that people are getting some use out of these instructions. I have crank windows now and don't have my pics of this project because I didn't even think of documenting it as an instructable when I was making my frames for the old windows. So I have to rely on my words, some drawings, and old pictures. My husband thinks I might have over-engineered the frames a little but I figure safety first!

i am wanting to do this in a pinch. I pulled a table up to window , stacked books, to prop ac up to level of sill. Taped a painting in window and cardboard to fill gaps. But, the water wouldn't drip out window because it was tilted toward the sill , inside. Hence not platform.... Now i have dismantled. Suggested to me to use siding inside of painting which is framed. Does siding come in slabs rather that strips, i wonder. Any suggestions. I'll watch the video in How To steps you provided. I want to see how to sit my ac onto the sill. I dont see a platform here in pic, and that's usually how it's done.

Hi, My window space is 17 3/8. Do you have any suggestions for me? I am desperate. It is very hot this week and Friday will be 101, maybe higher too due to humidity. I am going to buy a 5000 btu unit and am hoping to somehow get this in this space. There is not enough space to frame it. I could place a wood frame above the unit but how to hold the unit to this frame is the question. Plywood would of course cover the frame.

starshipminivan do you have any suggestions? Thanks for your help or anyone else who has any ideas.

Oh dear, I see that I did not respond to this comment when it was originally posted. I hope you found some relief. In that situation, where width is tight, I'd simply build a bracket to mount to the house which would support the unit, if possible.

You screw through the outside piece (the vertical ones as shown in the picture) into the horizontal piece. Deck screws, which I probably should have pointed out by giving their dimensions, are very long and sturdy and should have no problem securing the two pieces in this way.

What I meant was how do you hold the wood together to screw them? Screwing together two 2x4's when they are perpendicular to each other is kinda hard. Do you put them in a vice? Do you glue them beforehand then screw them? Do you get other people to hold the wood while you screw them?

It was a little more challenging because I only had warped 2x4's. Perhaps I got lucky because everything fit ok. Needed a little tweaking here & there.

My cross-piece in the center had to stick out a little toward the front to accommodate the A.C. unit. Stapling the screen to the back worked fine. I worked with some bracket steel and made little holders that the cover board slid into on the bottom, and fashioned some twist latches on the top corners to make installing and removing the board easier.

Thanks again. It is SO hot. The swamp cooler just doesn't work anymore. Now our bedroom is our little oasis.

This may be a silly question but can I just use plastic to fill in the extra room around my air conditioner hose? I have a standing unit and a side ways opening window, so instead of using wood to fill in the top I just used a big sheet of plastic, will this work?

For my portable air conditioner--the kind with the hose--I have a piece of plexiglass that's made to fit my window opening with the hole for the hose. So, yes. The plexi was cut and framed to replace the window screen during the summer months. It was done at the local glass shop. Since most of my windows have the same size screen, it can be moved around between each of the windows.

I don't think it would simply because, you're right, the standard air conditioners are larger than this, even the tiny little 5,000BTU units are something like 16" wide. The 2x4 frame actually narrows the width of the window opening (depending on the window framing itself) but you could probably build a metal frame that would not narrow down the opening of the window any more. However, the size of the air conditioners are still the problem here.

Thanks for the great instructable. I had the same dilemma, and some websites mentioned a solution was to build an "interior frame" but I wasn't clear on what that entailed. Your detailed diagrams helped me finish building this yesterday, and I had my first pleasant night in 2 months. I'll be putting up plexi, (got a temporary cover over the top right now), and I still need to weatherstrip the (sizeable) gaps, but all-in-all, it turned out great.

I can live with it for two months out of the year and I think a lot of other people feel that way too. I've been in beautiful houses that are hot hellholes in the summer. My guests would be more offended if I didn't have air conditioning because my 2nd story gets quite hot without it. Once built, I can install and uninstall it in a few minutes which is its beauty.

As soon as I saw how much more expensive the sliding/casement-style AC units were (3-4 times as expensive as the ones intended for double-hung windows!), I thought 'someone has already solved this problem'.

Thanks for the link! That cost issue is precisely why I built these frames. My air conditioners worked just fine, so why buy replacements when you can fit a square peg into a round hole with a little bit of lumber and time? Enjoy your air conditioner.

It looks good, but a word of warning.... You should really be protecting the outside of the window frame or else it will rot. And yes even if the window is underneath a porch or gutter this should be a concern. I just replaced a window frame because of that. I've done this differently over the years btw. Keep in mind that the A/C is what you are trying to hold up, NOT the plywood. With that being said I generally don't put any sides on the plywood. You screw the plywood to the top bracket on the a/c... screw a 1x4 on each side of the plywood on the frame side, thus wedging both boards tight against the window frame which makes the plywood sturdy enough to hold the weight of the A/C the bottom hooks on the ac are put on the inside of the frame, NOT the middle, thus giving the angle we need for drainage. Pool noodles or somehting similar are put on the window glass side of the plywood and the L-brackets supplied with the ac are used to clamp the window tight against the plywoood. The benefits of this method are the fact that the plywood is inside the window frame, which looks better, and the plywood is only as wide as the a/c, which gives you more window and thus more light.

I do hope you understand this is a temporary installation, despite its sturdiness. It should go in when the warm weather hits and be removed after, which is how most people do their installs. I believe this is the beauty of this projects--that, once built, the a/cs can be installed and removed in minutes once the frame is built. (I have a pet peeve about the tarped-over window air conditioners that I sometimes see in the middle of winter that are not only leaking in cold air but leaving the windows open to the elements.) Common-sense cautionary tales aside, the plywood is NOT the most important part of the install on this frame. Perhaps in the instructable you will likely author for installing an air conditioner, it is, but in the case of mine, it is not. Actually, it is the whole point of this project NOT to lean the air conditioner against the frame of the window or wedge it into the window itself in any way. In my project, the wood frame is crucial in both holding the a/c in place without using the window frame itself, which can be damaged if used in this way, to bear the weight AND in maintaining the proper drainage angle. It is this frame that is screwed into solid wood so the a/c isn't leaning against the window or sitting on the bottom rail of the window, which it can damage. With this framing method, you DO need lumber underneath the unit to allow for this narrow lip to sit against the frame and not on the ledge itself. If you read these instructions, the bottom lip IS inside the frame, not in some "middle" area. The top and bottom lip of the air conditioner itself are installed on the unit in a manner that, when mounted in a double-hung window according to its design, will coordinate so as to create at least the minimum angle necessary for the a/c to drain. So when it it placed in the frame, it will create at least this angle (which is, by the way, 15 degrees). Unlike the plywood-wedge method, my instructable addresses the ability to change the angle at which a particular unit will tip by changing the location of the framing piece that the top lip sits against.

Yeah, it's seriously ugly. It's normally not too bad though as I keep miniblinds on that window under a curtain and the blinds cover the plywood. I thought it would be fun to paint our college football team's logo on the plywood that faces out. I also have some hard insulation that I was thinking of adhering to the other side of the plywood with foam-friendly construction adhesive. I can still paint it--just have to make sure I use latex pint. Another idea I had was to create kind of shade or mini awning for the outside of the A/C to keep it running efficiently when the sun is beating down.

About This Instructable

Bio:I'm a Renaissance woman. I love to create things with a fantasy, medieval, or geeky edge. I'm also a math/science nerd. I have a passion for all things Halloween. I like to build props, create costume...read more »